For All Aerodynamics Lovers

F duct

F1 is finally back this weekend to Spa, a favourite circuit to many F1 fans and drivers. Lots of curiosity and excitement arised over the cars’ upgrades after the summer break. It is expected that McLaren would use their new DDRS design in Spa, together with Lotus further exploring their DDRS after the last two races before summer break. So huge focus is on DDRS again, which was introduced by Mercedes at the beginning of the season…

DRS

Let’s have a look at DRS first. DRS stands for Drag Reduction System. It was introduced to F1 in 2011 season, basically referring to adjustable flap on the rear wing. It’s a fairly simple system, as clearly illustrated in this 2011 video from Red Bull on both KERS and DRS. Jump to 1:24 for the DRS part.

KERS and DRS explanation

So when DRS is activated, the flap on the rear wing get flattened and therefore opens a slot at the rear wing, which produces a better streamlined shape of the car and consequently reduces both the downforce and the drag. Note that with the reduction of drag always comes along the sacrifice of downforce although the degree of reduction can be different. However, at long straights, less downforce is needed. By activating DRS, the car can boost 10 to 15 km/h extra top speed. DRS is allowed all the way in qualifying, but in races, only through overtaking zone when the a car is within 1 second to the front car after 2 laps is finished.

DDRS

As the words suggests, DDRS = DRS+DRS, a double drag reduction system. It was primarily developed by Mercedes, as one of the biggest innovations of 2012 season. In addition to the DRS system, Mercedes introduced a passive system which activates when DRS is open. It basically feeds the air from the rear wing and guide it through the cockpit to the front wing, therefore forms another DRS at the front part of the car.

Construction of Mercedes DDRS

The video below shows clearly how the air flows through the car:

Mercedes DDRS System

DDRS is very good for further reduction of drag on the straights, it more importantly gives the car good aero balance. In F1, aero balance is very important to guarantee stability – the ratio of downforce produced on the front and rear wing should be roughly the same as the car front and rear weight distribution. DRS is normally used on straights as it would be dangerous to use at corners with an unbalanced car, whereas DDRS has a potential to be used in less curved corners, also allowing the driver to activate it earlier after corners before going onto straights.

How does Mercedes DDRS work? – History and Analysis

We might need to go through some history here. It’s widely acknowledged that the design of DDRS is inspired by the F duct of McLaren in 2010, which is a great application of passive ducting system fighting against those rules set by FIA.

A bit off topic.. if you look through the innovations in f1 technology history, what engineers have been doing can be summarised as ‘finding the flaws of F1 rules’! 2009, double diffuser; 2010, F duct; 2011, exhaust blown diffuser – all banned after one season of usage. However, the idea of passive ducting system has been inspiring engineers since 2008, being modified every year based on the rules.

For your information on F duct, as a genesis of DDRS:

How does F duct work

So the experience from F ducts tells us:

Slots on the wing can be used to disturb air flow, therefore stall the wing to reduce drag (Note: stall of F1 wings means a reduction of downforce and drag rather than lose of all lift force on airplane wings)

It’s beneficial ducting the air

Passive system is a clever choice to gain downforce/ reduce drag without violating the rule

These are taken into Mercedes DDRS design, in which the air is guided from the rear wing through the channel along the car, exit at the front and cause front wing stall – A clever passive system which only operates when DRS is activated.

Question still exists on how the air flows exactly out of the slots. Generally speaking, engineers add slots to the wing either to generate more downforce or to reduce drag depending on the direction of the slot. In this case, we’re focusing on reducing drag, in which the direction of air flow should disturb natural flow, causing flow separation in order to stall the wing.

It’s suspected that besides the F duct idea, Mercedes DDRS is also related to their W duct design in 2011 on their front wing, which guide the air into the nose and feed it into different parts of the front wing

W duct of Mercedes W02 in 2011

The point here is that by blowing air underneath the front wing, you’d be able to increase the maximum angle of attack allowed for the car to run. Basically engineers increase the angle of attack to increase downforce until a critical angle of attack is reached, in which case the wing stalls and no more downforce can be generated. The blown air has a positive effect on increasing this angle, therefore allow higher downforce to be generated. So the slot here in W duct aims to increase downforce. It’s uncertain whether this now works along with Mercedes DDRS system so that more downforce is generated when DRS is inactive while stall occurs when DRS is active – considering aero balance, there is actually not too much downforce required on the front wing. Nevertheless, opening slots on the front wing could be an inspiration for Mercedes when developing their DDRS this year.

However, the use of DDRS system didn’t make Mercedes the fastest car in F1. It seems to work well in qualifying while not showing any benefit in Sunday races. The effect of stalling the front wing is quite controversial, even though the advantage of aero balance, top speed increase and passive activation still looks really appealing.

Lotus Passive Pylon Duct

After Mercedes, Lotus brought out a completely different DDRS design that instead of reducing drag at the front wing, it further reduces drag at the rear. Since FIA has clearly banned F duct design that uses slots at rear wing, Lotus places the slot at the connection between the rear wing and the engine. This would also cause wing stall and is passively activated by DRS beyond a certain air speed. As this system is only tested in the last two races, no consensus is reached yet on how it works exactly. However I’ll keep updates on this system.

I’m very curious on what kind of DDRS system McLaren is going to use. It’s expected and should be completely different from the Mercedes and Lotus systems. DDRS system, especially Mercedes one, is actually very difficult to copy since it requires the change of whole monocoque. Like all the previous innovations, DDRS is likely to be banned in 2013 F1 season although the official announcement has not come out yet. Let’s see what can happen to DDRS in the rest of 2012.

Spa is in fact one of the most ideal circuit for DRS application – capable of reducing lap time by 1.2s! So get excited for the race this weekend!

A F1 car is made of thousands of components and nearly every part need to take aerodynamics into consideration. However, there’re some major aerodynamics components that make huge difference to car aerodynamic performance.

Example of F1 Car Major Components – Exploded View of a BMW

These aero components get mentioned again and again in various F1 technical analysis assuming that people know what they are, but the fact is most people have no idea on those terms! I’m going through some major ones starting from the front of the car to the rear.

Front Wing

The first part we see on the front is definitely the front wing. Being the first means that it’s the first part on the car that interacts with the air, therefore having an important job to determine the under stream flow through the rest of car. The front wing generates 25% to 40% total downforce. Major design modification lies on the endplates and flaps of the wing, aiming to reduce tip vortex and wake of front wheel, which is one of the biggest drag components. In addition, ducts and slots are becoming popular in recent years, as can be seen in Mercedes W duct in 2011 and DDRS in 2012.

Sophisticated Front Wing Flaps and Endplate of MP4-27

Barge Board

This are vertical panels located between the front wheels and sidepods. It deals with the dirty air produced by the front wheels, guiding and smoothing air flow into the sidepod. In recent years’ designs, it may also have the function of feeding more air into the diffuser.

Ferrari F2012 Side-view: Barge Board in White

Sidepod

Sidepod is the part alongside the cockpit that accommodates the radiator and engine exhaust. Main Function of Sidepod is to 1) cool down the engine and gearbox; 2) control underbody flow to generate desired downforce. The profile of sidepods are varied significantly on different cars based on different aerodynamics configuration. A memorable design is McLaren L-shaped sidepod on MP4-26 in 2011.

MP4-26 L-shaped Sidepod

Airbox

The opening channel above drivers head that guides fresh and cold air to the cylinder for cooling purpose. Nevertheless, besides the conventional aim of cooling, the air flow through airbox can be utilised to generate more downforce/reduce drag by guiding it later to the desired parts on the rear wing assembly. F duct is a good example making advantage of this air flow. It’s also suspected that the Lotus E20 DDRS/ Super DRS has a tricky design of ‘ear’ inside the airbox.

‘Ear’ Inside Lotus E20 Airbox to Help Guiding the Air

Rear Wing

With the use of F duct and DRS, rear wing is always under spotlight in recent seasons. We’re talking about rear wing assembly here which normally consists of two sets of airfoil. The upper set is the main downforce generator including DRS, while the lower set is known as the beam wing. The whole rear wing sets generate to 30% to 40% total downforce.

Adjustable Rear Flap (DRS)

Flap on the rear wing whose angle of attack can be adjusted by the driver in order to reduce drag. Check out more about DRS here.

F duct

A driver controlled drag reduction system, in which a slot gap is opened on the rear wing flap. This air flow through the gap is able to stall the wing, therefore reducing drag.

Beam Wing

A single element wing at the lower part of the rear wing that helps regulate the air below the upper rear wing sets and improves diffuser performance. As F duct mounted on the upper flap is banned, there is now more aerodynamics consideration taken into the beam wing design. E.g. Lotus DDRS system which utilise beam wing to further reduce drag.

Source: Sutton Image

Lotus E20 Rear Wing Assembly

Gurney Flap

An L-shaped strip along the trailing edge of the wing, commonly on rear wings. With the use of gurney flap, flow separation can be delayed at high angle of attack so that more downforce can be generated. Gurney are used more in wet weather where more grip (downforce) is needed. FIA regulates that Gurneys on the rear wing should not exceed 20mm.

Source: ScarbsF1

Gurney flap along the edge of rear wing

Diffuser

The rear element at the underbody of F1 car close to the floor, from which air exits the car. This is the last components where air interacts with the car. The speed of air flow can significantly influence downforce, whereby the faster the flow exits, the more downforce is generated. Most famous designs in recent years are Brawn GP double diffuser in 2009 and exhaust blown diffuser which many teams used in 2011.